Minimally invasive procedures, for example laparoscopic surgical interventions, were originally performed via several small openings. For example, an endoscope was inserted through a central access opening and medical instruments were inserted through one, two, or more lateral access openings. The arrangement of an endoscope centrally and of two instruments from the side is also occasionally referred to as triangulation. Increasingly, however, efforts are made to reduce the number of access openings. For example, in laparoscopic surgery only one central access opening is now used, through which an endoscope and as a rule several instruments are inserted simultaneously. For reasons of space, these instruments cannot be completely straight. With straight instruments whose middle portions are positioned in a small access opening, the comparatively voluminous operational devices at the proximal ends make it difficult or impossible to move the distal ends together. Therefore instruments with a curved shaft have been developed.
Curved shafts for surgical instruments are described in WO 2006/100658 A2, in EP 2 087 834 A1, and in DE 20 2009 007 592 U1.
Curved shafts can constitute a marked improvement over straight shafts, in particular in minimally invasive procedures with several instruments in a single access opening. There remains, however, a mutual obstruction among the instruments, in particular concerning the distal ends with the tools, the center portions of the shafts that are positioned in the access opening, and the proximal ends of the instruments with operational devices. Medical staff must constantly keep this potential or actual mutual obstruction in mind in operating the instruments. This means, for one thing, that part of the medical staff's attention is always directed at careful and anticipatory operation of the medical instruments and, for another thing, that certain movements of the medical instruments must be avoided because of space restrictions or cannot be performed. Neither situation is tolerable for medical staff who need to function with concentration, efficiency, and the avoidance of exhaustion.